1. Field of the Invention
The invention relates to a intermittently operating sorption apparatus with a solid-matter absorbent for heat and cold storage. The basic components of such an apparatus are a storage vessel having a solid absorbent, an evaporator and/or a condenser for a working medium. The working medium is circulated through the above components within a pressure-resistant conduit system.
2. Description of the Background
In recent times, valve and/or pump devices have typically been added to pressure-resistant conduit systems to control the intermittent operation of a working medium. Regardless of whether this conduit system is operated at negative pressure or high pressure relative to the atmosphere valve and/or pump devices are expensive and often subject to malfunctioning and they are a possible leakage source. An example of this type of technology is given in German patent disclosure document DE-OS No. 3,207,656 (see reference numerals 13, 18, 19, 42 in FIG. 2 of the reference) or European patent document No. A 2-0,026,257 (see 382a, 390a, 388, 341, 386a in FIG. 3 of the reference). A fundamental survey of quite recent date on this technology is provided by the article entitled, "Zeolith-Wasser: Neues Stoff-paar fur Warmepumpen und Warmespeicher" (Zeolite/ Water: A New Substance Pair for Heat Pumps and Heat Storage Means), in the journal CCI 2/1984. A basic functional description in thermodynamic terms is also provided by the article entitled, "Thermochemical Heat Storage and Heat Transformation with Zeolites as Absorbents", in Proc. IEA Conf. on New Energy Conservation Technologies and Their Commercialization, Berlin, Apr, 6-10, 1981, J. P. Millhone and E. H. Willis, eds., Springer Verlag, Berlin--Heidelberg--New York, publishers (1981), Vol. 1, page 796.
In this type of known apparatus, the evaporator and the condenser have also been combined into an evaporator/condenser structural unit (U.S. Pat. No. 4,250,720, see reference numeral 14). However, a corresponding valve device (reference numerals 18, 19 of the patent) continued to be used at the hydraulic connection with the storage vessel (reference numeral 16 of the latter patent). In this prior art apparatus, the control of the operating phases can be performed by the valve device actuating or shutting off a heat source provided on an absorber/desorber. The result, however, is a compulsory return flow of the working medium vapor unless the valve device in the primary system is previously closed. Exact control of the operating phase is therefore possible only by means of this valve device located in the primary loop.
There is a considerable history of the construction of sorption storage apparatuses. Taking the basic thermodynamic function of the above components as a point of departure, continuous flow connections have already been provided between the storage vessel and an evaporator/condenser. By means of example, the following references can be cited in chronological order, U.S. Pat. No. Re. 5,287 (1873), U.S. Pat. No. 992,560 (1911) and German Pat. No. 738,333 (1943), which utilize water as the liquid sorption agent and ammonia as the working medium in the latter patent and a solid matter sorption agent in the two earlier patents.
Technological development of sorption apparatus having solid absorbents practically ceased in the 1940s and early 1950s (German Pat. Nos. 522,887 (1931), 722,164 (1942) and 814,157 (1951) and French Pat. No. 1,018,022 (1952)). All of these earlier known apparatuses also have an evaporator/condenser. These prior art apparatuses have the basic disadvantage that the sorption agent is immediately recharged with a working medium as soon as the supply of heat is interrupted in the desorption phase. As a consequence, neither the cold nor the heat generated, which heat in these previously known apparatuses is solely used as waste heat, can be stored for any significant length of time.
Moreover, evaporator/condensers are disadvantageous in principle. In the evaporation phase, the specific heat of the evaporator/condenser, along with the working medium it contains, must be brought from the condensation temperature to the cooling temperature in the first step. As a result, refrigerating capacity is lost to the cold consumer or absorber.
Similarly, in the desorption phase, the evaporator/condenser along with the remaining working medium contained in it must be heated to the condensation temperature. Thus, this thermal capacity is lost to any heat consumer or absorber present in the system. This latter aspect is admittedly secondary in apparatuses of this generic type because any heat that is produced is merely destroyed as waste heat. Nevertheless, the efficiency of combination evaporator/condensers is lower in principle than that of separate than that of the aggregate of evaporators and condensers.
The above-described old technology wherein a storage vessel, a condenser and an evaporator are in flow communication came to a dead end for the stated reasons. Interest shifted then to a valve control system as described supra. In such system, the evaporation of the working medium in the condenser during the absorption phase and the condensation of the working medium in the evaporator during the desorption phase, can be prevented.
The point of departure for the invention is a known, intermittently operating sorption storage apparatus with a solid absorbent according to German patent disclosure document DE-OS No. 3,212,608 which is structurally similar to the apparatus of this invention. In this known apparatus, however, the operating phases are also controlled by control devices, e.g., control valves and pumps in the primary system of the working medium. Thus, all the problems fundamentally associated with such features in the previously described technology remain.
Accordingly, there is still a need for a sorption storage apparatus which avoids the problems associated with the prior art valve devices in the primary system while at the same time storing heat or cold, or both, for relatively long periods of time and precisely controlling the operating phases.